Method and device for machining contoured recesses defined by csg

ABSTRACT

In a method for machining a contoured recess, a digital control is used to predetermine elementary surfaces, which are linked in a contouring expression using logical operators to form a resulting surface. Various help types are offered to the user on a graphical user interface of the digital control. The operators are explained using graphic symbols and help text. The resultant surface is represented on the user interface.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for machining contourpockets and to a device for machining contour pockets.

BACKGROUND INFORMATION

[0002] The machining of contour pockets is a common task in themachining of workpieces by a machine tool. Such contour pockets areproduced with the aid of a machine tool controlled by a numericalcontrol unit, e.g., by milling a workpiece. In this context, regions ofthe workpiece surface are machined, which are defined at the start ofeach instance of contour-pocket machining. Further, typical machiningsteps for producing a contour pocket then include, for instance, roughdrilling, reaming, and finishing.

[0003] The defining of the contour pocket may not be a simple task, assoon as the shape of the contour pocket is more complicated than thesimplest geometric figures, such as a circle, rectangle, or triangle.Islands may also be left inside the contour pockets, and the borders ofthe contour pockets may be as complicated as needed.

[0004] Conventional numerical control units already offer functions fordefining contour pockets. However, these functions do not optimallysupport the user in achieving his or her objective. In the handbookregarding the software of numerical control unit TNC 426 of theApplicant of the present application, a method is described by which acontour pocket can be defined. To this end, borders of surfaces aredefined, which are then rough-worked in a separate cycle. Whether theborder describes a pocket or an island depends on the direction and thecutter-radius correction of a border. The contour pocket ultimatelyformed is then the sum of all pockets minus the sum of all islands. Acertain amount of experience is necessary for using this system todefine complicated contour pockets, e.g., those made up of several basicshapes. In addition, the contour pocket to be expected can only beassessed in a simulation run after completion of the programming.

[0005] It is described in European Published Patent Application No. 0477 398 that, for the purpose of correcting the cutter radius,complicated workpiece geometries can be produced from more simple baseshapes, using set operations (union, intersection, etc.), since then,the cutting-radius correction can already be undertaken on the simplerbase shapes.

[0006] An aspect of the present invention may provide a method formachining contour pockets, which may allow even inexperienced users toproduce contour pockets in a rapid and error-free manner.

[0007] An aspect of the present invention may provide a device, whichmay allow rapid and error-free machining of contour pockets.

SUMMARY

[0008] In accordance with an example embodiment of the presentinvention, in order to machine a contour pocket with the aid of anappropriately equipped numerical control unit, at least a first and asecond elementary surface be specified in a first step, which are thencombined by an operator in a contour expression in a second step to forma combined or compound surface. After the evaluation of the operationand the calculation of the surface resulting from the contourexpression, the resulting surface is displayed in a graphic userinterface.

[0009] In this context, the user of this method for machining a contourpocket, or the user of an appropriately equipped device, may profit fromadditional support. Elementary surfaces, whose combination may alreadybe monitored on the user interface during the programming of thenumerical control unit, may now be used as a starting point whendefining the surface of a contour pocket. Errors may immediately bedetected and corrected. The selection of the correct operation issupported by corresponding softkeys, and by the display of help text.

[0010] Further aspects of example embodiments of the present inventionand details pertaining thereto are derived from the followingdescription of the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 illustrates a workpiece having a contour pocket.

[0012]FIG. 2 illustrates the surface of a contour pocket.

[0013]FIG. 3 illustrates a machine tool having a numerical control unit.

[0014]FIG. 4 illustrates different operations involving two elementarysurfaces.

[0015]FIG. 5 illustrates a method for machining a contour pocket.

[0016]FIG. 6 illustrates a user interface including further operationsinvolving elementary surfaces.

DETAILED DESCRIPTION

[0017]FIG. 1 shows a workpiece 1 having a contour pocket 2, whichcontains two islands 3.1 and 3.2. As illustrated in FIG. 2, the surfaceof contour pocket 2 is formed by taking the union of two elementarysurfaces 4 (in this example, two circular surfaces 4 and 5) and thentaking the intersection of this union and the complement of a square 6and the complement of a triangle 7. The intersection of a surface andthe complement of another surface may also be seen as the calculation ofthe difference of the two surfaces. In the example, square 6 andtriangle 7 are subtracted from the union of the two circular surfaces 4and 5. Actual contour pocket 2 of workpiece 1 is then formed, forexample, by milling it.

[0018] Such milling is carried out by a machine tool 8, as isillustrated in FIG. 3. Workpiece 1 is mounted to a machining table 9.The relative movement of workpiece 1 and tool 10 causes tool 10 to beguided through workpiece 1, so as to remove material. In this context,the movable axes of machine tool 8 are controlled by a numerical controlunit 11. This numerical control unit 11 may also be used to generate themachining programs for machine tool 8. One aspect of this is theprogramming of the contour-pocket machining. The defining of the surfaceof contour pocket 2 may be considered to be the most important step forthis. Further steps include, for example, the selection of a suitabletool 10, the best reaming strategy, the machining depth, the desiredsurface quality, etc. However, in the following, the definition ofcontour pocket 2 shall only mean the definition of the surface of acontour pocket 2.

[0019] Numerical control unit 11 is provided with a video screen 12having a graphic user interface 17, as is later explained on the basisof FIG. 6. In order to allow user inputs, the numerical control unit isalso provided with a keyboard 13 and/or other input options. A memory 24is used to store all data required for carrying out the machining of theworkpiece. These data are processed and all necessary actions areinitiated in a processing unit 25.

[0020] To provide better understanding, the operators used for combiningelementary surfaces 4 are explained with the aid of FIG. 4. Of course,the result of such an operation, a combined surface, may be combinedwith an elementary surface 4 or a combined surface, using an operator.

[0021]FIG. 4a shows the union of a first surface A and a second surfaceB. This corresponds to a logical “A OR B” operation of the involvedsurfaces.

[0022]FIG. 4b shows the intersection of a first surface A and a secondsurface B. This corresponds to a logical “A AND B” operation of theinvolved surfaces.

[0023]FIG. 4c shows the intersection of a first surface A with thecomplement of a second surface B. This corresponds to a logical “A ANDNOT B” operation of the involved surfaces.

[0024]FIG. 4d shows the union of a first surface A and a second surfaceB, minus the intersection of A and B. This corresponds to a logical “(AOR B) AND NOT (A AND B)” operation of the involved surfaces, or a “AEXCLUSIVE OR B”, i.e., “A XOR B”, operation of the involved surfaces.

[0025] In addition to the operators defined here, there are alsoadditional, elements which allow a logical combination or operation ofelementary surfaces 4 in a contour expression. Thus, one may requireparentheses, in order to be able to preferentially calculate parts ofthe contour expression, as well as an operator for forming thecomplement of an elementary surface 4.

[0026] A method for defining a contour pocket 2 shall now be describedin light of FIG. 5. In this context, reference is also made to theelements of a numerical control unit 11 and its graphic user interface17 required for this, which are illustrated in FIG. 3 and FIG. 6.

[0027] As may be conventional, the method for defining a contour pocket2 begins with a step 101 for defining at least two elementary surfaces4. To this end, boundary 19, which encloses elementary surface 4, may bedefined, for example, in a subroutine. Thus, a circular surface may bedefined by the coordinates of the center point and the radius, or atriangular surface may be defined by specifying the coordinates of thevertices. To this end, the subroutine may be input into numericalcontrol unit 11 via keyboard 13 and stored in memory 24. Elementarysurfaces 4 may also have borders 19 that are markedly more complex thanthe simple geometric elements used in the examples. It is possible touse elementary surfaces 4 having an unclosed border 19, for instance, ahalf-plane cut off by a straight line. Elementary surfaces defined oncemay be used again to define a further contour pocket, e.g., by beingcalled up by the subroutine stored in memory 24.

[0028] In a next step 102, elementary surfaces 4 are combined byoperators 20. In this context, at least two elementary surfaces 4 arecombined by operators 20 in a contour expression 14. Operators 20 havingthe logical function “OR”, “AND”, “AND NOT”, and “EXCLUSIVE OR” are, forexample, available. Numerical control unit 11 also accepts parentheses22, in order to preferentially evaluate parts of contour expression 14.To form a “NOT” operator 20 for calculating the complement of anelementary surface 4 or of a combined surface 21 (e.g., a part ofcontour expression 14 put in parentheses 22). Softkeys 15, which allowspecific operator 20 or a parenthesis 22 to be selected, are provided onvideo screen 12 of numerical control unit 11, in graphic user interface17. These softkeys 15 contain picture symbols 23, which schematicallyexplain specific operator 20 (in the manner of FIGS. 4a-d). In addition,help text 16 is displayed in graphic user interface 17, as soon as anoperator 20 is selected. Contour expression 14 is stored in memory 24 ofnumerical control unit 11, via keyboard 13.

[0029] Subsequent step 103 may be taken after each change of contourexpression 14. Contour expression 14 is evaluated and a resultingsurface 18 is calculated in processing unit 25 of numerical control unit11. This resulting surface 18 corresponds to the surface of contourpocket 2. In this context, contour expression 14 may be so completelycomplex, that several contour pockets 2 not connected to each other areformed. Even such a resulting surface 18 may be defined again as anelementary surface 4, which may then be further utilized in othercontour expressions 14. Thus, it again becomes clear that an elementarysurface 4 must not necessarily be simple.

[0030] In a further step 104, resulting surface 18 is displayed ingraphic user interface 17 on video screen 12 of numerical control unit11. In this context, resulting surface 18 is represented as a filled-inborder 19, in order to allow resulting surface 18 to be rapidlycomprehended. However, elementary surfaces 4 are only represented bytheir border 19. In graphic user interface 17, both contour expression14 and resulting surface 18 may be shown at the same time, asillustrated in FIG. 6.

[0031] A further combination of elementary surfaces 4 is explained withthe aid of FIG. 6. In contour expression 14, operands QC4 and QC5 denoteelementary surfaces 4, in this case a rectangle and triangle, which arecombined by operator 20 “OR” to form a first combined surface 21. In thesame way, QC1, QC2, and QC3 denote circles, which are combined byoperator 20 “OR”. Because of parentheses 22, the two combined surfaces21 are preferentially evaluated in processing unit 24. The two combinedsurfaces 21 are connected by the operator “AND NOT”, so that the threecombined circular surfaces QC1, QC2, and QC3 are subtracted from theunion of rectangle QC4 and triangle QC5. In FIG. 6, resulting surface 18is illustrated, as well as the help text 16 for “AND NOT” operator 20last used, and softkeys 15 having their picture symbols 23.

[0032] When steps 103 and 104 are executed each time, as soon as achange is made to contour expression 14 in step 102, a user of numericalcontrol unit 11 is provided as much support as possible for defining acontour pocket 2.

[0033] The further machining of contour pocket 2 may be accomplished ina conventional manner, in that numerical control unit 11 controlsmachine tool 8 so as to produce, in workpiece 1, a contour pocket 2having the shape of resulting surface 18. The machining steps necessaryfor this may include, more or less, rough drilling, reaming, andfinishing with the aid of suitable tools 10.

1. to
 19. (Canceled).
 20. A method for machining contour pockets of a workpiece, comprising: specifying at least a first elementary surface and a second elementary surface to a numerical control unit; displaying softkeys, which correspond to operators and which include picture symbols that explain the operators, on a graphic user interface of the numerical control unit; inputting a contour expression using the operators via the graphic user interface; combining the first elementary surface with the second elementary surface in the contour expression using the operators to form a combined surface; evaluating the contour expression and calculating a surface resulting from the contour expression; and displaying the resulting surface in the graphic user interface.
 21. The method according to claim 20, wherein the combining step includes forming further combinations of the elementary surfaces and the combined surface in the contour expression.
 22. The method according to claim 20, wherein the combining step includes at least one of: a union of a first surface and a second surface; an intersection of the first surface and the second surface; an intersection of the first surface and a complement of the second surface; and a union of the first surface and the second surface minus an intersection of the first surface and the second surface.
 23. The method according to claim 20, wherein the contour expression includes at least one pair of parentheses, the contents of the parentheses preferentially calculated in the evaluating step.
 24. The method according to claim 20, wherein the contour expression includes an operator to form a complement of one of: (a) the combined surface; and (b) at least one of the elementary surfaces.
 25. The method according to claim 20, further comprising, after selection of an operator, displaying help text on the graphic user interface to explain the operator.
 26. The method according to claim 20, wherein the resulting surface is displayed in the resulting surface displaying step by a filled-in border.
 27. The method according to claim 20, wherein the contour expression includes a representation of the elementary surfaces only by a border of the elementary surfaces.
 28. The method according to claim 20, further comprising repeating the evaluating step and the resulting surface display step after every change to the contour expression.
 29. The method according to claim 28, further comprising displaying the contour expression and simultaneously the resulting surface, a change to the contour expression immediately resulting in a change in the displaying of the resulting surface.
 30. The method according to claim 20, further comprising controlling a machine tool by the numerical control unit to produce the contour pocket having a shape of the resulting surface.
 31. A numerical control unit for a machine tool, comprising: an arrangement configured to perform a method for machining contour pockets of a workpiece, the method including: specifying at least a first elementary surface and a second elementary surface to the numerical control unit; displaying softkeys, which correspond to operators and which include picture symbols that explain the operators, on a graphic user interface of the numerical control unit; inputting a contour expression using the operators via the graphic user interface; combining the first elementary surface with the second elementary surface in the contour expression using the operators to form a combined surface; evaluating the contour expression and calculating a surface resulting from the contour expression; and displaying the resulting surface in the graphic user interface.
 32. A numerical control unit for a machine tool, comprising: means for specifying at least a first elementary surface and a second elementary surface to the numerical control unit; means for displaying softkeys, which correspond to operators and which include picture symbols that explain the operators, on a graphic user interface of the numerical control unit; means for inputting a contour expression using the operators via the graphic user interface; means for combining the first elementary surface with the second elementary surface in the contour expression using the operators to form a combined surface; means for evaluating the contour expression and calculating a surface resulting from the contour expression; and means for displaying the resulting surface in the graphic user interface.
 33. A device for machining contour pockets, comprising: a numerical control unit configured to define the contour pockets; a video screen configured to display a graphic user interface; a memory configured to store data that relate to at least a first elementary surface and a second elementary surface and configured to store a contour expression, the data and the contour expression inputtable via a keyboard, the contour expression combining the elementary surfaces with each other using at least one operator; wherein the numerical control unit includes a processing unit configured to calculate a resulting surface from the contour expression; wherein the video screen is configured to display the resulting surface; and wherein the graphic user interface includes softkeys that include picture symbols that explain the operators, the operators of the contour expression selectable via the softkeys.
 34. The device according to claim 33, wherein the video screen is configured to display help text to explain the operator after the operator is selected.
 35. The device according to claim 33, wherein the video screen is configured to simultaneously display the contour expression and the resulting surface from the contour expression in the graphic user interface. 